Radio-frequency identificaton (rfid) antenna, tags and communications systems using the same

ABSTRACT

Radio-frequency identification (RFID) tag antenna, tags and communications systems using the same are presented. The RFID tag antenna includes a patterned conductive loop having a plurality of longitudinal conductive sections and a pair of transverse conductive sections connecting to each end of the longitudinal conductive sections to serve as a matching network. A pair of extended conductive arms is electrically connected to the patterned conductive loop via two nodes. A bonding pad with an RFID chip disposed thereon is arranged at the central area of the pair of extended conductive arms.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from aprior U.S. Provisional Application No. 61/088,083, filed on Aug. 12,2008, the entire contents of which are incorporated herein by reference.

This application is based upon and claims the benefit of priority from aprior Taiwanese Patent Application No. 097148160, filed on Dec. 11,2008, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The disclosure relates to radio-frequency identification tag devices,and in particular, to radio-frequency identification (RFID) tagantennas, tags and communications systems using the same.

2. Description of the Related Art

Radio-frequency identification (RFID) systems have been applied in manyfields such as in supply chain management, security, tracking and othercommercial applications. Thus, RFID innovative developments have beendriven by users wanting to improve upon the technology, such as in thesupply chain management process. The RFID systems allow transparencythroughout the distribution chain including manufacturers, suppliers,distributors and retailers, providing information such as product type,location, date, etc. One of the greatest benefit of RFID systems is toimprove upon supply chain management efficiency, as an example. Atpresent, most product information is recorded in barcodes, and theinformation is then retrieved by scanning the barcode using a scanner.Meanwhile, the RFID tag antennas can be detected within a certain range,and a large amount of information can be processed simultaneously.

However, the shortcomings of the design and application of conventionalRFID tag antennas are that the fabrication costs thereof are expensive.At present, costs for RFID tag antennas take the largest proportionamong costs of RFID devices. Recently, process improvements have beenmade to lower fabrication costs of the RFID tag antenna. For example,RFID tag antenna conductors can be made of silver paste using theroll-to-roll manufacturing process or screen printing process or otherprinting methods to reduce fabrication costs. In the fabricating processhowever, the amount of silver paste required is a key portion of thetotal fabrication material cost of the RFID tag antenna.

U.S. Pat. No. 7,277,017, the entirety of which is hereby incorporated byreference, discloses an RFID tag antenna, implemented by a dipoleantenna (dipole) tag antenna or a Central Loop (loop) consisting of aconductor.

FIG. 1 is a schematic plan view illustrating a conventional RFID tagantenna. Referring to FIG. 1, in the conventional RFID tag antenna 10,an antenna pattern 12 is formed on the substrate 11. An IC chip 13 isdisposed on the antenna pattern 12. The antenna pattern 12 can serve asa dipole antenna which includes two singular pole patterns 121 and 122.Each of the two singular pole patterns 121 and 122 extends outwardlyfrom the position of the IC chip 13. The antenna pattern 12 furtherincludes a correction loop 123 to compensate or adapt to antennacharacteristics. The correction loop 123 bypasses the position of the ICchip 13 and connects to the two singular pole patterns 121 and 122.

FIG. 2 is a schematic plan view illustrating another conventional RFIDtag antenna. Referring to FIG. 2, in the conventional RFID tag antenna10, an antenna pattern 12 is formed on the substrate 11. An IC chip 13is disposed on the antenna pattern 12 which includes a loop antenna. Twoextension portions 12 a and 12 b extend outwardly from the position ofthe IC chip 13. The two extension portions 12 a and 12 b arerespectively connected to the IC chip 13 and a correction loop 123. TheIC chip 13 is further connected to a conductive pattern 16. Both sidesof the correction loop 123 respectively include dual patterns 123 a and123 b which purpose to remove the parasitic capacitance between the ICchip 13 and the antenna pattern 12.

However, the inductance generated by the loop antenna does noteffectively eliminate the capacitance generated between the conductorand the IC chip. Furthermore, controlling RFID tag antenna resonancefrequencies for conventional RFID tag antennas is difficult.

BRIEF SUMMARY

An exemplary embodiment of the disclosure provides a radio-frequencyidentification (RFID) tag antenna, comprising: a patterned conductiveloop having a plurality of longitudinal conductive sections and aplurality of transverse conductive sections connecting to each end ofthe longitudinal conductive sections to serve as a matching network; apair of extended conductive arms electrically connected to the patternedconductive loop via two nodes; and a bonding pad with an RFID chipdisposed thereon arranged at the central area of the pair of extendedconductive arms.

Another exemplary embodiment of the disclosure provides aradio-frequency identification (RFID) tag device, comprising: asubstrate; a patterned conductive loop disposed on the substrate, thepatterned conductive loop having a plurality of longitudinal conductivesections and a plurality of transverse conductive sections connecting toeach end of the longitudinal conductive sections to serve as a matchingnetwork; a pair of extended conductive arms electrically connected tothe patterned conductive loop via two nodes; and a bonding pad with anRFID chip disposed thereon arranged at the central area of the pair ofextended conductive arms.

Another exemplary embodiment of the disclosure provides aradio-frequency identification (RFID) communications system, comprising:an RFID tag device; a read antenna sensing the RFID tag device; and amicroprocessor processing and transmitting a signal sensed by the readantenna. The RFID tag device comprises: a substrate; a patternedconductive loop disposed on the substrate, the patterned conductive loophaving a plurality of longitudinal conductive sections and a pair oftransverse conductive sections connecting to each end of thelongitudinal conductive sections to serve as a matching network; a pairof extended conductive arms electrically connected to the patternedconductive loop via two nodes; and a bonding pad with an RFID chipdisposed thereon arranged at the central area of the pair of extendedconductive arms.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a schematic plan view illustrating a conventional RFID tagantenna;

FIG. 2 is a schematic plan view illustrating another conventional RFIDtag antenna;

FIG. 3 is a schematic plan view of an exemplary embodiment of an RFIDtag antenna of the disclosure;

FIG. 4 is a schematic plan view of another exemplary embodiment of theRFID tag antenna of the disclosure;

FIG. 5 is a schematic equivalent circuit diagram illustrating anexemplary embodiment of the RFID tag antenna; and

FIG. 6 is a schematic block diagram illustrating an exemplary embodimentof a radio-frequency identification (RFID) communications system.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent exemplary embodiments, or examples, for implementing differentfeatures of various embodiments. Specific examples of components andarrangements are described below to simplify the present disclosure.These are merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself indicate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation method for a first feature over or on a secondfeature in the description that follows may include embodiments in whichthe first and second features are formed in direct contact or not indirect contact.

Main features and key aspects of exemplary embodiments of the disclosureprovide a radio-frequency identification (RFID) tag antenna, tag devicesand communications systems. Since the cost of an RFID tag device ismainly dependent on the antenna design, there is a need to reduceproduction costs of the antenna. In addition, the conductor materialsbased on the antenna design includes aluminum, etched copper, silverpaste formed by screen printing, combined with roll-to-rollmanufacturing processes. In one exemplary embodiment, the gain of theRFID tag antenna can reach at least 1.42 dBi. Furthermore, the RFID tagantenna includes a special impedance matching network which can adjustlocation of the impedance matching network, thereby facilely controllingthe antenna resonance frequency.

FIG. 3 is a schematic plan view of an embodiment of an RFID tag antennaof the disclosure. Referring to FIG. 3, an RFID tag device 300 includesa substrate 301 and an antenna pattern 312 formed on the substrate 301.The substrate 301 includes a rigid substrate, a flexible substrate, apaper, a fabric, composites thereof, or combinations thereof. Forexample, the substrate can be made of a glass fiber material (FR4), orpolyethylene terephthalate (PET), polyimide (PI), or other soft or hardpolymer substrates. According to another exemplary embodiment of thedisclosure, the substrate comprises a high permittivity material or ahigh permeability material. The antenna pattern 312 is not limited tobeing formed on the substrate 301. It can be alternatively orselectively embedded in the substrate 301.

The antenna pattern 312 includes a patterned conductive loop 318disposed on the substrate 301. The patterned conductive loop 318includes a plurality of longitudinal conductive sections 315 a -315 fand a plurality of transverse conductive sections 313 a,313 b and 313 cconnecting to each end of the longitudinal conductive sections to serveas a matching network. Note that the width and spacing of eachlongitudinal conductive sections 315 a -315 f are dependent on realisticdesign requirements of the antenna characteristics. A pair of extendedconductive arms 325 a and 325 b are disposed on the substrate to serveas a dipole antenna and are electrically connected to the patternedconductive loop 318 via two nodes 316 a and 316 b. The pair of extendedconductive arms 325 a and 325 b can be a pair of tapered dipole antennaswhich width becomes thinner outwardly from the central area. Accordingto another exemplary embodiment of the disclosure, the antenna pattern312 further includes a pair of second conductive segments 326 a and 326b respectively connected to a thinner end of the pair of tapered dipoleantennas 325 a and 325 b, wherein the pair of second conductive segmentsare substantially perpendicular to the pair of tapered dipole antennasor are extended along any included angle, and wherein a length and awidth of the pair of second conductive segments are dependent upon theimpedance and frequency response of the RFID chip. A bonding pad 320with an RFID chip disposed thereon is arranged at the central areabetween the pair of extended conductive arms 325 a and 325 b.

In order to comply with internal impedance matching of radio-frequencyidentification (RFID) chips, some embodiments of the disclosure derivevarious antenna impedance matching networks with two nodes electricallyconnected to the pair of tapered dipole antennas to optimize impedancematching of the antenna and to achieve excellent resonance effect.

Note that the RFID tag antenna pattern 312 may be adopted by anydifferent conductor materials, such as copper, copper paste, silverpaste, aluminum and the likes, achieving frequency response of 902-928MHz and bandwidth of 50 MHz, or alternatively achieving frequencyresponse of 860-960 MHz.

FIG. 4 is a schematic plan view of another exemplary embodiment of theRFID tag antenna of the disclosure. Referring to FIG. 4, an RFID tagdevice 400 includes a substrate 401 and an antenna pattern 412 formed onthe substrate 401. The substrate 401 includes a rigid substrate, aflexible substrate, a paper, a fabric, composites thereof, orcombinations thereof. For example, the substrate can be made of a glassfiber material (FR4), or polyethylene terephthalate (PET), polyimide(PI), or other soft or hard polymer substrates. According to anotherexemplary embodiment of the disclosure, the substrate comprises ahigh-permittivity material or a high permeability material. The antennapattern 412 is not limited to being formed on the substrate 401. It canbe alternatively or selectively embedded in the substrate 401.

The antenna pattern 412 includes a patterned conductive loop 418disposed on the substrate 401. The patterned conductive loop 418includes a plurality of longitudinal conductive sections 415 a -415 hand a plurality of transverse conductive sections 413 a, 413 b, and 413c connecting to each end of the longitudinal conductive sections toserve as a matching network. Note that the width and spacing of eachlongitudinal conductive sections 415 a -415 h are dependent on realisticdesign requirements of antenna characteristics. A pair of extendedconductive arms are disposed on the substrate to serve as a dipoleantenna and are electrically connected to the patterned conductive loop418 via two nodes 416 a and 416 b. The pair of extended conductive armscan be a pair of parallel dipole antennas 425 a, 435 a, and 425 b, 435b. Each parallel dipole antenna is separated with a predeterminedspacing. The pair of parallel dipole antennas 425 a, 435 a, and 425 b,435 b respectively has a node 430 a, 430 b connected therebetween,wherein a distance a between the node and the center of the pair ofparallel dipole antennas is dependent upon the impedance and frequencyresponse of the RFID chip. According to another exemplary embodiment ofthe disclosure, the antenna pattern 412 further includes a pair ofsecond conductive segments 426 a and 426 b respectively connected to anend of the pair of dipole antennas 425 a and 425 b, wherein the pair ofsecond conductive segments are substantially perpendicular to the pairof tapered dipole antennas or are extended along any included angle, andwherein a length and a width of the pair of second conductive segmentsare dependent upon the impedance and frequency response of the RFIDchip. A bonding pad 420 with an RFID chip disposed thereon is arrangedat the central area between the pair of extended conductive arms 425 aand 425 b.

FIG. 5 is a schematic equivalent circuit diagram illustrating anexemplary embodiment of the RFID tag antenna. In FIG. 5, eachlongitudinal conductive section of the conductive loop can be severalstripes of perpendicular metal conductive materials. The length of theinductor and the number of the vertical conductors can be adjusted. Theinductors indicated as L1, L2, L3, L4, and the inter-inductance L5between the inductors, and the inductance L6 of the antenna are composedof common impedance. The common impedance and the impedance of the RFIDchip 450 results in conjugate impedance matching, thereby increasingantenna resonance response and antenna transmission efficiency.

FIG. 6 is a schematic block diagram illustrating an exemplary embodimentof the radio-frequency identification (RFID) communications system.Referring to FIG. 6, a radio-frequency identification (RFID) tagcommunications system 500, including an RFID tag device 510, an antenna520 for reading the RFID tag device, and a microprocessor 530 processingand transmitting the signal read by the sensing antennas. Theabove-mentioned radio-frequency identification (RFID) tag communicationssystem 500 has many applications such as supply chain management, accesscontrol card, and warehouse management system on a UHF waveband.Moreover, in the Gen2 specification, there are dual mode sensingfunctions, wherein a dual sensing mode is generated for both the far endand the close end of passive RFIDs. Advantages of various embodiments ofthe RFID antenna, tags and communications systems using the same of thedisclosure are as follows. First, antenna performance is maintained.Also, the cost of the tag antenna is reduced. Next, adaptability of theantenna is improved. Specifically, a special adaptive matching networkis designed and an adaptive adjusting RFID device is applicable for UHFcentral frequencies, i.e., matching the multiple impedances of the RFIDdevice. Thus, conjugate matching and maximum energy transmission isachieved.

While the disclosure has been described by way of example and in termsof the exemplary embodiments, it is to be understood that the disclosedembodiments are not limitative. To the contrary, it is intended to covervarious modifications and similar arrangements (as would be apparent tothose skilled in the art). Therefore, the scope of the appended claimsshould be accorded the broadest interpretation so as to encompass allsuch modifications and similar arrangements.

1. A radio-frequency identification (RFID) tag antenna, comprising: apatterned conductive loop having a plurality of longitudinal conductivesections and a plurality of transverse conductive sections connecting toeach end of the longitudinal conductive sections to serve as a matchingnetwork; a pair of extended conductive arms electrically connected tothe patterned conductive loop via two nodes; and a bonding pad with anRFID chip disposed thereon, arranged at the central area between thepair of extended conductive arms.
 2. The RFID antenna as claimed inclaim 1, wherein the pair of extended conductive arms is a pair oftapered dipole antennas which width becomes thinner outwardly.
 3. TheRFID antenna as claimed in claim 2, further comprising a pair of secondconductive segments respectively connected to a thinner end of the pairof tapered dipole antennas, wherein the pair of second conductivesegments are substantially perpendicular to the pair of tapered dipoleantennas or are extended along any included angle, and wherein a lengthand a width of the pair of second conductive segments are dependent uponthe impedance and frequency response of the RFID chip.
 4. The RFIDantenna as claimed in claim 1, wherein the pair of extended conductivearms is a pair of parallel dipole antennas with a predetermined spacingtherebetween.
 5. The RFID antenna as claimed in claim 4, wherein thepair of parallel dipole antennas has a node connected therebetween, andwherein a distance between the node and the center of the pair ofparallel dipole antennas is dependent upon the impedance and frequencyresponse of the RFID chip.
 6. The RFID antenna as claimed in claim 1,wherein the patterned conductive loop comprises electroplated copper,electroplated aluminum, silver paste, or copper paste.
 7. The RFIDantenna as claimed in claim 1, wherein the patterned conductive loopcomprises etched copper or etched aluminum.
 8. A radio-frequencyidentification (RFID) tag device, comprising: a substrate; a patternedconductive loop disposed on the substrate, wherein the patternedconductive loop has a plurality of longitudinal conductive sections anda plurality of transverse conductive sections connecting to each end ofthe longitudinal conductive sections to serve as a matching network; apair of extended conductive arms electrically connected to the patternedconductive loop via two nodes; and a bonding pad with an RFID chipdisposed thereon, arranged at the central area of the pair of extendedconductive arms.
 9. The RFID tag device as claimed in claim 8, whereinthe substrate comprises a rigid substrate, a flexible substrate, apaper, a fabric, or combinations thereof.
 10. The RFID tag device asclaimed in claim 8, wherein the substrate comprises a high permittivitymaterial or a high permeability material.
 11. The RFID tag device asclaimed in claim 8, wherein the patterned conductive loop is embedded inthe substrate.
 12. The RFID tag device as claimed in claim 11, whereinthe pair of extended conductive arms is a pair of tapered dipoleantennas which width becomes thinner outwardly.
 13. The RFID tag deviceas claimed in claim 12, further comprising a pair of second conductivesegments respectively connected to a thinner end of the pair of tapereddipole antennas, wherein the pair of second conductive segments issubstantially perpendicular to the pair of tapered dipole antennas orare extended along any included angle, and wherein a length and a widthof the pair of second conductive segments are dependent upon theimpedance and frequency response of the RFID chip.
 14. The RFID tagdevice as claimed in claim 8, wherein the pair of extended conductivearms is a pair of parallel dipole antennas with a predetermined spacingtherebetween.
 15. The RFID tag device as claimed in claim 14, whereinthe pair of parallel dipole antennas has a node connected therebetween,and wherein a distance between the node and the center of the pair ofparallel dipole antennas is dependent upon the impedance and frequencyresponse of the RFID chip.
 16. The RFID tag device as claimed in claim8, wherein the patterned conductive loop comprises electroplated copper,electroplated aluminum, silver paste, or copper paste.
 17. The RFID tagdevice as claimed in claim 8, wherein the patterned conductive loopcomprises etched copper or etched aluminum.
 18. A radio-frequencyidentification (RFID) communications system, comprising: an RFID tagdevice, comprising: a substrate; a patterned conductive loop disposed onthe substrate, wherein the patterned conductive loop has a plurality oflongitudinal conductive sections and a plurality of transverseconductive sections connecting to each end of the longitudinalconductive sections to serve as a matching network; a pair of extendedconductive arms electrically connected to the patterned conductive loopvia two nodes; and a bonding pad with an RFID chip disposed thereonarranged at the central area between the pair of extended conductivearms; a read antenna sensing the RFID tag device; and a microprocessorprocessing and transmitting a signal sensed by the read antenna.
 19. TheRFID communications system as claimed in claim 18, wherein the pair ofextended conductive arms is a pair of tapered dipole antennas whichwidth becomes thinner outwardly.
 20. The RFID communications system asclaimed in claim 19, further comprising a pair of second conductivesegments respectively connected to a thinner end of the pair of tapereddipole antennas, wherein the pair of second conductive segments aresubstantially perpendicular to the pair of tapered dipole antennas orare extended along any included angle, and wherein a length and a widthof the pair of second conductive segments are dependent upon theimpedance and frequency response of the RFID chip.
 21. The RFIDcommunications system as claimed in claim 18, wherein the pair ofextended conductive arms is a pair of parallel dipole antennas with apredetermined interval therebetween.
 22. The RFID communications systemas claimed in claim 21, wherein the pair of parallel dipole antennas hasa node connected therebetween, and wherein a distance between the nodeand the center of the pair of parallel dipole antennas is dependent uponthe impedance and frequency response of the RFID chip.